JP5178800B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to a sheet conveying apparatus that corrects a skew of a sheet and a position in a width direction of the sheet and an image forming apparatus including the sheet conveying apparatus.

  In general, in an image forming apparatus such as a copying machine, a printer, or a facsimile, a conveyed sheet is skewed, or a deviation occurs in a width direction position (hereinafter also referred to as a “lateral registration position”) orthogonal to the sheet conveyance direction. Then, an image is formed on the sheet in a state where the image position is shifted. Therefore, the sheet conveying apparatus of the image forming apparatus is provided with a skew correction unit for aligning the posture and position of the sheet before conveying the sheet to the image forming unit.

  The skew correction unit is generally provided on the upstream side of a transfer unit that transfers an image to a sheet. For example, the skew correction unit is based on a side registration standard that corrects a positional deviation of the sheet with reference to a side edge of the sheet being conveyed. Sheet skew correction is performed (see Patent Document 1).

  The skew correction unit for correcting the skew of the sheet based on the side registration reference is provided with an abutting reference member along the sheet conveyance direction on one side of the sheet conveyance path, and a plurality of skew feeding roller pairs on the sheet conveyance path. Place. The abutting reference member has a reference surface substantially parallel to the sheet conveyance direction, and the plurality of skew feeding roller pairs are arranged in the sheet conveyance direction along the reference surface. Then, the sheet being conveyed is obliquely fed to the abutting reference member side by the pair of skew feeding rollers, the width is brought close, and the side edge of the sheet is abutted against the reference surface and along the reference surface, whereby the sheet in the conveying direction is aligned. Correct the tilt. Further, since the position of the sheet side end portion in the direction orthogonal to the sheet conveying direction can be defined by the reference plane, the positional deviation in the sheet width direction can also be corrected based on the position of the reference plane.

  However, as shown in FIG. 18A, when the sheet S is sandwiched between the pair of first inclined feeding rollers 32a positioned at the most upstream, a force Fp acting on the center of gravity of the sheet S in the direction opposite to the sheet conveying direction is generated. Occur. When the distance from the center of gravity to the sheet side end is Lp, a moment M (= Fp × Lp) that tries to turn in the direction of the arrow shown in FIG. To do. The sheet is swung by this moment M, and the skew is corrected by the side end portion of the sheet S hitting the abutting reference member 31. At the same time, the side end portion of the sheet S is bent.

  As described above, the conventional skew correction unit has an excessively strong pressing force of the sheet against the reference surface (width-shifting force by the skew feeding roller) when the side end portion of the sheet is abutted against the reference surface of the abutting reference member. In such a case, the sheet may be bent and the sheet may be jammed or the correction accuracy may be reduced.

  For this, the nip pressure (clamping pressure) of the skew feeding roller is changed to adjust the pressing force of the sheet side edge against the reference surface, and the sheet side edge is aligned with the reference surface without bending the sheet. A sheet conveying apparatus that corrects skew is disclosed (see Patent Document 2).

JP-A-11-189355 JP-A-5-246588

  However, although the sheet conveying apparatus described in Patent Document 2 can adjust the pressing force to the abutting reference member by adjusting the nip pressure of the skew feeding roller pair by the correction method based on the side registration standard, the skew feeding correction is possible. May not be enough. For example, when the stiffness of a sheet such as ultra-thin paper (coated paper having a basis weight of less than 80 gsm) (hereinafter, also referred to as “koshi”) is low, or in a high-temperature and high-humidity environment where the stiffness of the sheet is lowered by humidity, the following Such a problem may occur.

  A plurality of skew feeding roller pairs are arranged in the sheet conveying direction, and when the upstream feeding roller pair that first feeds the sheet obliquely sandwiches the sheet, the sheet turns and hits the reference surface of the abutting reference member. As a result, the side edge of the sheet is bent. In the case of a sheet with high rigidity, this bending is returned due to the stiffness of the sheet, but in the case of a sheet with low rigidity, the bending is not returned, and is held between the next pair of skew feeding rollers, and the amount of bending generated in the sheet conveying direction is large. The skew correction is insufficient due to the difference (deflection difference). In particular, as shown in FIG. 18B, when the sheet S is conveyed in a state where it is nipped by a plurality of skew feeding rollers, it is difficult for the deflection to return, and when the sheet S is conveyed to the third skew feeding roller. There was a risk that the flexure would buckle (break) and cause a paper jam (jam).

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet conveying device having a skew feeding correction unit capable of performing stable skew feeding correction regardless of the type of sheet, and an image forming apparatus including the same.

The present invention, in Cie over preparative conveying apparatus to correct the skew of the sheet to convey the sheet conveying path, a first pair of inclined feeding rollers which separably to feed obliquely shea over preparative, before Symbol first skew provided in the sheet conveyance direction downstream side of the rollers, the sheet on which the first pair of inclined feeding rollers to feed obliquely and second oblique-feed rollers to feed obliquely, in the sheet conveyance direction downstream side of the second oblique-feed rollers provided, and a third pair of inclined feeding rollers where the second pair of inclined feeding rollers to feed obliquely the sheet feeding obliquely disposed along the sheet conveying direction, the side edge of the sheet which is oblique-feed by the oblique feed roller pairs the are brought into contact with the reference member to correct the skew of the sheet, after the sheet conveyed by pre-Symbol first skew roller pair has reached the second oblique-feed rollers, by the first pair of inclined feeding rollers before said sheet conveyed passes through the first pair of inclined feeding rollers, and the third skew row Characterized by comprising a control unit which Ru is separated the first pair of inclined feeding rollers before reaching the pair.

  As in the present invention, the second skew feeding roller pair sandwiches the sheet skewly fed by the first skew feeding roller pair, and further, before reaching the third skew feeding roller pair, the first skew feeding roller pair. Release the nipping of the sheet by separating the rollers. Thus, stable sheet skew correction can be performed regardless of the type of sheet, usage environment, and the like.

1 is a cross-sectional view schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. (A) is a top view which shows the state in which a sheet | seat is conveyed diagonally along a conveyance roller part, (b) is a top view which shows the state in which a sheet | seat turns in a skew correction part. (C) is a plan view showing a state in which a skew-corrected sheet is conveyed by a pair of registration rollers, and (d) shows a state in which a subsequent sheet is conveyed while being skewed on a conveyance roller unit. It is a top view. FIG. 5A is a cross-sectional view schematically showing a state where the conveyance roller pair holds the sheet, and FIG. 5B is a cross-sectional view schematically showing a state where the conveyance roller pair releases the sheet. It is sectional drawing which shows the state which the 3rd skew feeding roller pair clamped the sheet | seat. (A) is sectional drawing which shows the nip state of the conveyance roller pair which concerns on this embodiment, (b) is sectional drawing which shows the nip cancellation | release state of a conveyance roller pair. It is a perspective view which shows the drive part of the conveyance roller part which concerns on this embodiment. It is a top view which shows the drive part which drives the skew feeding roller pair of the skew feeding correction part which concerns on this embodiment. (A) is a perspective view explaining the moving mechanism of the driven roller which comprises the skew feeding roller pair which concerns on this embodiment, (b) is a side view explaining the moving mechanism of a driven roller. (A) is a figure which shows the nip state of the skew feeding roller pair which concerns on this embodiment, (b) is a figure which shows the nip cancellation | release state of a skew feeding roller pair. (A) is a top view which shows the state which the sheet | seat which carried out the skew feeding correction part which concerns on this embodiment passes, (b) is a top view which shows the state by which skew feeding of a sheet | seat is correct | amended. . It is A arrow directional view of the skew feeding correction | amendment part shown in FIG.10 (b). FIG. 6 is a plan view showing a state in which a sheet is skew-corrected by a skew correction unit according to the embodiment. It is a figure for demonstrating the relationship of the nip pressure of the 1st-3rd skew feeding roller pair of the skew feeding correction part which concerns on this embodiment. FIG. 4 is a block diagram of a controller that performs nip pressurization and release by n skew feeding roller pairs included in a skew feeding correction unit according to the present embodiment. It is a flowchart which shows skew feeding correction | amendment operation | movement in case the skew feeding correction part which concerns on this embodiment has three skew feeding roller pairs. It is a flowchart which shows skew feeding correction | amendment operation | movement when the skew feeding correction part which concerns on this embodiment cancels | releases only the nip of a 1st skew feeding roller pair. It is a flowchart which shows skew feeding correction | amendment operation | movement in case the skew feeding correction part which concerns on this embodiment has n skew feeding roller pairs. (A) and (b) are diagrams illustrating a sheet that is skew-corrected by a skew-feeding correction unit provided in a sheet conveying device of a conventional image forming apparatus.

  Hereinafter, an image forming apparatus including a sheet conveying apparatus according to an embodiment of the present invention will be described with reference to the drawings. The image forming apparatus according to the present embodiment includes a sheet conveying apparatus having a sheet aligning unit that corrects the skew of the conveyed sheet and the position in the width direction of the sheet, such as a copying machine, a printer, a facsimile, and a composite device thereof. An image forming apparatus.

  The image forming apparatuses are mainly classified into a tandem method in which a plurality of image forming units are arranged side by side and a rotary method in which a plurality of image forming units are arranged in a cylindrical shape. Transfer methods are classified into a direct transfer method in which a toner image is directly transferred from a photosensitive drum to a sheet, and an intermediate transfer method in which the toner image is once transferred to an intermediate transfer member and then transferred to a sheet.

  The intermediate transfer method does not require the sheet to be held on the transfer belt unlike the direct transfer method, and thus can be used for a wide variety of sheets such as ultra-thick paper and coated paper. Further, it is suitable for realizing high productivity due to the features of parallel processing in a plurality of image forming units and batch transfer of full-color images. Therefore, in the following embodiments, description will be made using an intermediate transfer type image forming apparatus 100 in which four color image forming units are arranged on an intermediate transfer belt.

  First, the overall configuration of the image forming apparatus 100 according to the present embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the overall configuration of an image forming apparatus 100 according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 100 </ b> A that configures the appearance of the image forming apparatus 100. In the apparatus main body 100A, an image forming unit 513, a sheet feeding unit 100B for feeding the sheet S, a transfer unit 100C for transferring the toner image formed by the image forming unit 513 to the sheet S, and the sheet S are conveyed. And a sheet conveying unit 100D as a sheet conveying apparatus.

  The image forming unit 513 includes a photosensitive drum 508, an exposure unit 511, a developing unit 510, a primary transfer unit 507, a cleaner unit 509, and the like, yellow (Y), magenta (M), cyan (C), and black (Bk). ) Image forming unit. Note that the colors formed by each image forming unit are not limited to these four colors, and the order of color arrangement is not limited to this.

  The sheet feeding unit 100 </ b> B includes a sheet storage unit 51 that stores sheets S stacked on the lift-up unit 52, and a sheet feeding unit 53 that sends out the sheets S stored in the sheet storage unit 51. . Examples of the sheet feeding unit 53 include a method using frictional separation by a paper feed roller and the like, a method using air separation and adsorption, and the like. In the present embodiment, a paper feeding method using air is used. It has been.

  The transfer unit 100C is stretched by rollers such as a driving roller 504, a tension roller 505, a secondary transfer inner roller 503, and a secondary transfer roller 56, and is intermediately transferred by an intermediate transfer belt 506 that is transported in the direction of arrow B shown in FIG. Is provided. A toner image formed on the photosensitive drum is transferred to the intermediate transfer belt 506 by a predetermined pressure and an electrostatic load bias given by the primary transfer unit 507. The toner image transferred to the intermediate transfer belt 506 is subjected to a predetermined pressurizing force and an electrostatic load bias applied by a secondary transfer portion 515 constituted by a secondary transfer inner roller 503 and a secondary transfer roller 56 that are arranged to face each other. Thus, the sheet S is adsorbed as an unfixed image.

  The sheet conveying unit 100D includes a conveying unit 54 that conveys the sheet S, a sheet aligning unit 150, a registration roller pair 7, a pre-fixing conveying unit 57 that conveys the sheet S to the fixing unit 58, a branch conveying path 59, A reverse conveyance path 501 and a double-side conveyance path 502 are provided. The conveyance unit 54, the pre-fixing conveyance unit 57, the branch conveyance path 59, the reverse conveyance path 501, the double-side conveyance path 502, and the like constitute a sheet conveyance path.

  Note that a large number of conveyance roller pairs are arranged in the conveyance unit 54, the branch conveyance path 59, the reverse conveyance path 501, and the double-side conveyance path 502. These conveying roller pairs are configured to convey the sheet S when the driving roller and the driven roller rotate while the sheet S is sandwiched between the driving roller and the driven roller. Further, these conveying roller pairs set a nip pressure for nipping the sheet S between the two rollers by urging the driven roller toward the driving roller by an urging member such as a spring (not shown).

  The sheet aligning unit 150 includes a conveyance roller unit 50 and a skew feeding correction unit 55, and corrects the skew of the sheet S and the position of the sheet S in the width direction. The registration roller pair 7 includes a driving roller and a driven roller that is in pressure contact with the driving roller and conveys the sheet together with the driving roller, and conveys the sheet S to the secondary transfer unit 515 at a predetermined timing.

  1 is a controller as a control unit that controls an image forming operation of the image forming apparatus 100 and a skew feeding correcting operation of a sheet to be described later.

  Next, an image forming operation of the image forming apparatus 100 according to the present embodiment will be described. The sheets S are fed one by one by the sheet feeding unit 53 at a predetermined image forming timing, and are conveyed to the sheet aligning unit 150 through a conveyance path 54 a included in the conveyance unit 54. In the sheet alignment unit 150, skew correction and timing correction are performed, and then the sheet S is sent to the secondary transfer unit 515 at a predetermined timing in the registration roller pair 7.

  At this time, in the image forming unit 513, the photosensitive drum 508 is rotated in the direction of arrow A shown in FIG. 1, and the photosensitive drum 508 is uniformly charged by a charging unit (not shown). Thereafter, the exposure unit 511 issues a signal to the rotating photosensitive drum 508 based on the image information signal sent thereto. By irradiating this light via the reflecting means 512 or the like, an electrostatic latent image is formed on the photosensitive drum 508. Note that the toner slightly remaining on the photosensitive drum 508 is collected by the cleaner unit 509 and prepared for the next image formation again.

  Once the electrostatic latent image is formed on the photosensitive drum 508, toner development is performed on the electrostatic latent image by the developing unit 510, and a toner image is formed on the photosensitive drum 508. The toner image formed on the photosensitive drum 508 is given a predetermined pressure and an electrostatic load bias by the primary transfer unit 507, and the toner image is transferred onto the intermediate transfer belt 506. Note that image formation by the yellow, magenta, cyan, and black image forming units of the image forming unit 513 is performed at a timing when the toner image is superimposed on the upstream toner image primarily transferred onto the intermediate transfer belt 506. As a result, a full-color toner image is finally formed on the intermediate transfer belt 506.

  The full-color toner image formed on the intermediate transfer belt 506 is transferred to the sheet S sent to the secondary transfer unit 515 at a predetermined timing by the registration roller pair 7. The sheet S on which the full-color toner image has been transferred is conveyed to the fixing unit 58 by the pre-fixing conveying unit 57, and the fixing unit 58 applies a heating effect by a predetermined pressurizing force and a heat source such as a heater, so that the toner image is formed. The toner image is fixed to the sheet S by melting.

  The sheet S on which the image is fixed is discharged onto the paper discharge tray 500 via the branch conveyance path 59. When images are formed on both sides of the sheet S, the sheet S is conveyed to the reverse conveyance path 501 by a switching member (not shown). As described above, when the sheet S is conveyed to the reverse conveying path 501, the leading and trailing ends of the sheet S are switched by performing a switchback operation, and are conveyed to the duplex conveying path 502.

  Thereafter, the sheet is merged from the refeed path 54b of the transport unit 54 in time with the sheet S of the subsequent job fed from the sheet feeding unit 100B, and is sent to the secondary transfer unit 515 as described above. Since the image forming process is the same as that of the first surface (one surface) described above, description thereof is omitted here. The sheet S on which the image is formed on the second surface (both surfaces) and the image is fixed is discharged onto the paper discharge tray 500 via the branch conveyance path 59.

  Next, the sheet aligning unit 150 provided in the sheet conveying unit 100D included in the image forming apparatus 100 according to the present embodiment will be specifically described with reference to FIGS. The sheet aligning unit 150 is disposed on the upstream side of the secondary transfer unit 515, and includes a conveyance roller unit 50 and a skew feeding correction unit 55 located on the downstream side of the conveyance roller unit 50.

  First, the conveyance roller unit 50 will be described with reference to FIGS. FIG. 2A is a plan view illustrating a state in which the sheet S is conveyed while being skewed on the conveyance roller unit 50. FIG. 2B is a plan view showing a state in which the sheet S is turned by the skew feeding correction portion 55. FIG. 2C is a plan view showing a state in which the skew-corrected sheet S is conveyed by the registration roller pair 7. FIG. 2D is a plan view showing a state in which the subsequent sheet S2 is conveyed while being skewed on the conveying roller unit 50. FIG. FIG. 3A is a cross-sectional view schematically illustrating a state in which the conveyance roller pair 34 sandwiches the sheet S. FIG. 3B is a cross-sectional view schematically showing a state in which the conveyance roller pair 34 has released the sheet S. FIG. 4 is a cross-sectional view illustrating a state in which the third skew feeding roller pair 32c sandwiches the sheet S.

  As shown in FIG. 2A to FIG. 4, the conveyance roller unit 50 includes a plurality of conveyance roller pairs 34 each having a driving roller 13 and a driven roller 14. The driven roller 14 is configured to be able to contact and separate (pressure contact and separation) with respect to the driving roller 13. The conveying roller pair 34 switches between a state in which the driving roller 13 and the driven roller 14 hold the sheet S and a state in which the holding of the sheet S is released by pressing or separating the driven roller 14 from the driving roller 13. It is configured to be possible.

  The driving roller 13 is made of a rubber material such as natural rubber or synthetic rubber, and the driven roller 14 is made of a synthetic resin material. In the following, the state in which the driving roller 13 and the driven roller 14 sandwich the sheet S is also referred to as “nip state”, and the state in which the sheet S is released is also referred to as “nip release state”.

  Next, the nip release mechanism of the conveyance roller pair 34 that shifts from the nip state to the nip release state will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5A is a cross-sectional view showing a nip state of the conveying roller pair 34 according to the present embodiment. FIG. 5B is a cross-sectional view illustrating the nip release state of the conveying roller pair 34.

  As shown in FIG. 5A, the driven roller 14 is rotatably supported on the arm member 101 via the driven shaft 20, and the arm member 101 is supported on the stay member 18 via the swing shaft 102. It is swingably supported. The arm member 101 is in contact with the drive roller 13 side by an eccentric roller 103, and the eccentric roller 103 is connected to a pre-registration pressure release motor (stepping motor) 104 through gear trains 105 and 106. ing.

  When separating the conveying roller pair 34, the pre-registration pressure release motor 104 is rotated to rotate the eccentric roller 103 via the gear trains 105 and 106, and the end portion of the arm member 101 is pressed by the eccentric roller 103. . As a result, the arm member 101 located at the position shown in FIG. 5A rotates about the swing shaft 102 in the nip releasing direction. Specifically, as shown in FIG. 5B, the driven roller 14 is lifted, the nip with the driving roller 13 is released, and the conveying roller pair 34 is separated. In the present embodiment, the nip release timing can be changed by rotating the pre-registration pressure release motor 104 in accordance with the detection timing of the pre-registration sensor P.

  Next, the drive part of the conveyance roller part 50 is demonstrated, referring FIG. FIG. 6 is a perspective view showing a drive unit of the transport roller unit 50 according to the present embodiment. As shown in FIG. 6, the rotational driving force from the pre-registration motor Mp is transmitted to the driving roller 13 through the pulley 302a and the belt 302 to the roller shaft 13b to which the driving rubber roller 13a is fixed. Note that the pre-registration motor Mp that is a drive unit that drives the drive roller 13 is a stepping motor, and the stop timing and rotation speed can be changed according to the timing of the pre-registration sensor P by the pre-registration motor Mp.

  The driven roller 14 is in a position where the driving roller 13 shown in FIG. 3A is pressed when the sheet S conveyed from the conveyance unit 54 is conveyed. As a result, after being conveyed from the conveyance unit 54, the sheet S is nipped by the plurality of conveyance roller pairs 34 and conveyed to first to third skew feeding roller pairs 32 a to 32 c described later included in the skew feeding correction unit 55. The On the other hand, after the sheet S reaches the most upstream first skew feeding roller pair 32a in the sheet conveyance direction of the skew feeding correction portion 55, before the sheet S reaches the downstream second skew feeding roller pair 32b, FIG. As shown in b), the driven roller 14 is separated from the driving roller 13. When the driven roller 14 is thus separated and the nip with the driving roller 13 is released, the sheet S is fed obliquely by the first to third skew feeding roller pairs 32a to 32c. It is possible to prevent the oblique feeding from being hindered by the conveying roller pair 34.

  Here, P shown in FIGS. 3A and 3B is an optical pre-registration sensor, and the pre-registration sensor P has a light emitting unit (not shown) and a light receiving unit (not shown). The pre-registration sensor P is configured to detect the passage timing of the sheet S by detecting light reflected on the sheet S by the light receiving unit when the sheet S passes.

  Next, the skew feeding correction unit 55 will be described with reference to FIGS. 7 to 9B in addition to FIGS. 2A to 3B. FIG. 7 is a plan view showing a drive unit that drives the first to third skew feeding roller pairs 32a to 32c of the skew feeding correction unit 55 according to the present embodiment. FIG. 8A is a perspective view for explaining a moving mechanism of the driven rollers 331a to 331b constituting the first to third skew feeding roller pairs 32a to 32c according to the present embodiment, and FIG. 8B is a driven roller. It is a side view explaining the moving mechanism of 331a-331b. FIG. 9A is a diagram illustrating a nip state of the first to third skew feeding roller pairs 32a to 32c according to the present embodiment, and FIG. 9B is a diagram illustrating the first to third skew feeding roller pairs 32a to 32c. It is a figure which shows the nip release state.

  The skew correction unit 55 according to the present embodiment performs skew correction based on a side registration reference that corrects a positional deviation of the sheet with reference to the side edge of the sheet S being conveyed. Further, the skew feeding correction unit 55 is disposed on the upstream side of the secondary transfer unit 515.

  As illustrated in FIG. 2A, the skew feeding correction unit 55 includes a fixed guide 33 that functions as a conveyance guide for the sheet S, and a width direction of the sheet according to the size of the sheet S to be conveyed (FIG. 2A And a skew feeding section 30 that is movable in the direction of arrow C). The skew feeding unit 30 includes a first skew feeding roller pair 32a, a second skew feeding roller pair 32b, and a third skew feeding roller pair 32c. The first to third skew feeding roller pairs 32a to 32c are sequentially arranged from the upstream side. Arranged along the sheet conveying direction.

  Further, the first to third skew feeding roller pairs 32a to 32c are arranged with respect to the sub-scanning direction (conveying direction) so as to obtain an abutting and conveying component with respect to a reference member 31 (described later) for positioning the side end portion of the sheet S. Inclined by an angle α and attached to the skew feeding part 30.

  As shown in FIGS. 3A and 3B, the first to third skew feeding roller pairs 32a to 32c are in contact with and separated from the driving rollers 332a to 332c and the driving rollers 332a to 332c (pressure contact and separation). Possible driven rollers 331a to 331b. The first to third skew feeding roller pairs 32a to 32c release the nipping state of nipping the sheet S and nipping the sheet S by causing the driven rollers 331a to 331b to be pressed against or separated from the driving rollers 332a to 332c. It is possible to switch to the nip release state. The driving rollers 332a to 332c are made of a rubber material such as natural rubber or synthetic rubber, and the driven rollers 331a to 331b are made of metal bearings.

  As shown in FIG. 7, the drive rollers 332a to 332c are connected to a pulley 326 via universal joints 321a to 321c, and the pulley 326 is connected to an oblique feed motor Ms via a conveyor belt 323 to 325. ing. The drive rollers 332a to 332c are driven by the skew feeding drive motor Ms thus connected. The oblique drive motor Ms is a stepping motor, and the stop timing and rotation speed can be changed according to a predetermined timing.

  As shown in FIGS. 8A and 8B, the driven rollers 331a to 331b include a link 332A, a pressure gear 334, a pressure spring 335, and a skew feeding pressure motor Mk. The link 332A rotatably supports the driven rollers 331a to 331b. The pressure spring 335 is provided between the link 332A and the pressure gear 334. The oblique pressure motor Mk rotates the pressure gear 334. The link 332A, the pressure gear 334, the pressure spring 335, and the oblique feeding pressure motor Mk constitute a moving mechanism for the driven rollers 331a to 331b.

  The first to third skew feeding roller pairs 32a to 32c rotate the pressure gear 334 by a predetermined angle by the skew feeding pressure motor Mk, thereby causing the nip pressure (sheet) between the driven rollers 331a to 331c and the driving rollers 332a to 332c. Set the clamping pressure. Specifically, when the driven rollers 331a to 331c are in pressure contact with the driving rollers 332a to 332c, the pressure gear 334 rotates in the direction of arrow D shown in FIG. 9A to pull the pressure spring 335. It has stopped in the state. The link 332A is pulled by the pressure gear 334 via the pressure spring 335. Then, by pulling the link 332A in this way, the driven rollers 331a to 331c are brought into pressure contact with the driving rollers 332a to 332c.

  On the other hand, at the time of releasing the nip, the pressure gear 334 is stopped in a state of rotating in the direction of arrow E shown in FIG. When the pressure gear 334 rotates in the direction of arrow E, the pressure gear 334 is configured to push in the link 332A via the link 333. The driven rollers 331a to 331c move in the direction of releasing the nip (upward as shown in FIG. 9B) by pushing the link 332A. The oblique feed pressure motor Mk is a stepping motor, and the nip pressures of the oblique feed roller pairs 32a to 32c can be changed by setting the step angle. In the present embodiment, since the moving mechanism is provided in each of the driven rollers 331a to 331c, the nip pressures of the skew feeding roller pairs 32a to 32c can be set independently.

  In addition, an abutting reference member 31 (hereinafter referred to as a “reference member”) on which the sheet S obliquely fed by the first to third skew feeding roller pairs 32 a to 32 c is abutted is provided in the oblique feeding portion 30. ing. The reference member 31 is provided with a reference surface formed substantially in parallel with the conveyance direction of the sheet S, and the side end portion of the sheet S which is obliquely fed by the first to third skew feeding roller pairs 32a to 32c is It abuts against this reference plane (see FIG. 11 described later).

  Next, the operation of the sheet aligning unit 150 according to the present embodiment will be described with reference to FIGS. 10 (a) to 13 in addition to FIGS. 2 (a) to 2 (d). FIG. 10A is a plan view showing a state in which the skewed sheet S passes through the skew correction unit 55 according to the present embodiment. FIG. 10B is a plan view showing a state in which the skew of the sheet S is corrected. FIG. 11 is a view taken along arrow A of the skew feeding correction unit 55 shown in FIG. FIG. 12 is a plan view showing a state in which the sheet S is skew-corrected by the skew correction unit 55 according to the present embodiment. FIG. 13 is a diagram for explaining the relationship between the nip pressures of the first to third skew feeding roller pairs 32a to 32c of the skew feeding correcting portion 55 according to the present embodiment.

  As shown in FIG. 2A, when the sheet S is conveyed from the conveyance unit 54 to the conveyance roller unit 50 with the skew angle β, the sheet S remains skewed by the conveyance roller pair 34. The state is conveyed to the skew correction unit 55. The sheet S conveyed to the skew feeding correction unit 55 is sandwiched between the first skew feeding roller pair 32a. When the sheet S is sandwiched between the first skew feeding roller pair 32a, the sheet S is moved to the first skew feeding roller pair. It is turned by 32a. The turned sheet S is conveyed obliquely toward the reference member 31 as shown in FIG. The nip of the conveying roller pair 34 is released after the sheet S reaches the first skew feeding roller pair 32a but before reaching the second skew feeding roller pair 32b.

  Next, when the sheet S obliquely fed by the first skew feeding roller pair 32a reaches the second skew feeding roller pair 32b and the second skew feeding roller pair 32b pinches the sheet S, the first skew feeding roller pair 32a. The nip N1 is released.

  At this time, as shown in FIG. 10A, since the sheet S is conveyed obliquely toward the reference member 31 by the first skew feeding roller pair 32a, the side end portion of the sheet S hits the reference member 31. In addition, a deflection difference ΔL between the front and rear ends occurs. However, as shown in FIG. 10B, the sheet S is released from the nip N1 of the first skew feeding roller pair 32a and is held only by the nip N2 of the second skew feeding roller pair 32b. The turning around the center becomes easy. Then, while turning around the nip N2, the correction to eliminate the deflection difference ΔL is performed by following the reference surface of the reference member 31.

  On the other hand, the skew of the sheet S is corrected by the above-described operation. However, as shown in FIG. However, as shown in FIG. 11, the deflection L slips at the nip N2 of only the second inclined feeding roller pair 32b due to the abutting reaction force R from the reference surface of the reference member 31, and the deflection L in the abutting direction is reduced. It is released (see FIG. 12). Further, when the skew feeding correction is not sufficient, the same skew feeding correction is performed by the third skew feeding roller pair 32c disposed on the downstream side of the second skew feeding roller pair 32b. improves. For example, in the case of ultra-thin paper such as coated paper having a basis weight of less than 80 (gsm), since the rigidity of the sheet in the abutting direction of the sheet S is weak, the bending difference ΔL and the bending L are gradually released. It is effective to correct the skew, and the above-described method is preferable.

  Here, the relationship between the nip pressures in the nips N1, N2, and N3 of the first to third skew feeding roller pairs 32a to 32c will be described with reference to FIG. As shown in FIG. 13, the nip pressure of the nip N1 of the first skew feeding roller pair 32a is P1, the nip pressure of the nip N2 of the second skew feeding roller pair 32b is P2, and the nip N3 of the third skew feeding roller pair 32c is The nip pressure is P3. At this time, if the nip pressures of the first to third skew feeding roller pairs 32a to 32c are set so as to increase toward the downstream side in the conveying direction of the sheet S as P1 ≦ P2 ≦ P3, the first to third The conveying force of the pair of skew feeding rollers 32a to 32c increases from the paper feeding side toward the paper discharging side.

  For example, in the second skew feeding roller pair 32b, the driving roller 332b is a rubber roller, and the opposed driven roller 331b is a metal bearing. Therefore, when the driven roller 331b is pressed by the driving roller 332b, the rubber portion of the driving roller 332b is crushed. In general, when the rubber roller is rotated at the same speed (angular speed), the sheet that is nipped by the crushing portion of the rubber roller becomes faster, and the higher the nip pressure (nipping pressure), the higher the sheet conveyance speed.

  When the nip pressure P2 of the second skew feeding roller pair 32b on the downstream side becomes P1 ≦ P2, the driving roller 332b of the second skew feeding roller pair 32b is crushed more than the driving roller 332a of the first skew feeding roller pair 32a. As a result, the rotation speed of the second skew feeding roller pair 32b is faster than that of the first skew feeding roller pair 32a, and the posture of the sheet S is set so that the posture of the swung sheet S becomes early and substantially parallel to the reference member 31. Can be corrected. Similarly, the posture of the sheet S can be further stabilized by setting P2 ≦ P3 for the third skew feeding roller pair 32c.

  Next, when the skew correction unit 55 abuts the sheet S against the reference surface of the reference member 31 and completes the skew correction of the sheet S, as shown in FIG. The roller pairs 32a to 32c release the nip. The sheet S from which the nip is released is conveyed by the registration roller pair 7 at a predetermined timing. In addition, as illustrated in FIG. 2D, the skew feeding unit 30 moves in a direction (width direction of the sheet S) orthogonal to the conveyance direction of the sheet S.

  Next, the controller 600 that performs nip pressurization by the first to third skew feeding roller pairs 32a to 32c and the release thereof that the skew feeding correction unit 55 has will be described. FIG. 14 is a block diagram of a controller 600 that performs nip pressurization by n skew feeding roller pairs included in the skew feeding correction unit 55 according to the present embodiment and release thereof.

  In the present embodiment, the skew feeding correction unit 55 having the first to third skew feeding roller pairs 32a to 32c has been described. However, n skew feeding roller pairs are provided as a plurality of skew feeding roller pairs. It can also be used in the skew correction unit. Therefore, here, the controller 600 when there are n skew feeding roller pairs will be described.

  As shown in FIG. 14, the controller 600 includes a CPU 601, a ROM 603 that stores programs and the like, a RAM 602 that temporarily stores data and the like, and an I / O 604 that is used for communication. The controller 600 inputs sheet information such as the size, basis weight (gsm), and the number of sheets to be passed by the user via the operation unit 412, so that the size, basis weight (gsm), and passage of the sheet S are input. Recognize the number of sheets.

  Further, the controller 600 uses the pre-registration sensor P via the AD conversion unit 605 and the pre-registration sensor Q via the AD conversion unit 610 to send the oblique pressure motors Mka to Mkn via the drivers 609a to 609n. To control. In other words, the nip pressurization and release of the driven roller of the pair of skew feeding rollers is performed by controlling the skew feeding pressure motors Mka to Mkn.

  Further, the skew feeding drive motor Ms is controlled via the driver 606, the pre-registration motor Mp is controlled via the driver 607, the pre-registration pressure release motor 104 is controlled via the driver 608, and the driven roller of the conveying roller unit 50 is controlled. 14 nip pressurization and nip release are controlled.

  Next, the skew correction operation of the skew correction unit 55 by the controller 600 according to the present embodiment will be described with reference to the flowcharts shown in FIGS. First, the skew correction operation when the skew correction unit 55 has three skew feeding roller pairs will be described. FIG. 15 is a flowchart showing the skew correction operation when the skew correction unit 55 according to the present embodiment has three skew feeding roller pairs.

  As shown in FIG. 15, when the basis weight (gsm), size, and number of sheets to be passed are input by the operation of the operation unit 412 by the user (step S01), the controller 600 displays the input sheet information. recognize. When the sheet information is recognized, the controller 600 determines a set value of the nip pressure (slope feeding pressure) of the first to third skew feeding roller pairs 32a to 32c according to the basis weight and size of the sheet S ( In step S02), paper feeding is started.

  Next, as shown in FIG. 3A, when the sheet S reaches the conveyance roller unit 50 and the pre-registration sensor P detects (ON) the leading edge of the sheet S (step S03), the controller 600 temporarily turns on the pre-registration motor Mp. Stop and adjust the time between sheets (variation in sheet conveyance time). On the other hand, if the pre-registration sensor P does not detect the leading edge of the sheet S in step S03, a paper jam (delay jam) is displayed on the operation unit 412 (step S17), and the process ends.

  When the adjustment of the time between sheets is completed, the pre-registration motor Mp is restarted and the sheet S is conveyed to the skew feeding unit 30 as shown in FIG. Specifically, at a timing before the leading edge of the sheet S reaches the skew feeding roller pair after the pre-registration sensor P detects (ON) the leading edge of the sheet S, the first to third skew feeding roller pairs 32a, 32b, The driven rollers 331a, 331b, and 331c of 32c are driven. Then, the nip of the first to third skew feeding roller pairs 32a, 32b, 32c is pressurized to the set value of the skew feeding pressure determined in step S02 (step S04). Note that the timing of pressurizing the nip may be all at the same time or sequentially pressurize from the upstream side in the transport direction.

  Next, after being conveyed to the oblique feeding unit 30, the driven roller 14 of the conveyance roller pair 34 of the conveyance roller unit 50 is driven to release all the nips of the conveyance roller pair 34, and the sheet S in the oblique conveyance unit 30 is released. Butt matching is started (step S05). Here, when the basis weight of the sheet S is less than 80 (gsm) (step S06), the controller 600 first transfers the first end after the sheet leading edge is nipped between the second skew feeding roller pair 32b and conveyed 10 mm. The nip of the skew feeding roller pair 32a is released (step S07).

  Similarly, the controller 600 releases the nip of the second skew feeding roller pair 32b after the leading edge of the sheet S is conveyed 10 mm after being nipped between the third skew feeding roller pair 32c (step S08). Here, the timing of releasing the nip between the first skew feeding roller pair 32a and the second skew feeding roller pair 32b is the time obtained by dividing the distance from the pre-registration sensor P to each skew feeding roller pair by the conveying speed in the skew feeding section 30. It is set by the soft count value. Thereafter, as shown in FIG. 4, the sheet S is nipped between the third skew feeding roller pair 32 c, and the abutting alignment of the sheet S is completed (step S <b> 10).

  On the other hand, when the basis weight of the sheet S is 80 (gsm) or more in step S06, the sheet S is abutted and aligned without releasing the nip of the first to third skew feeding roller pairs 32a to 32c (step S09). ).

  Next, when the registration roller front sensor Q detects (ON) the leading edge of the sheet S (step S11), the sheet S is nipped between the registration roller pair 7 and conveyed 10 mm (step S12), and then all the nips are detected. Is released (step S13). Then, a lateral slide operation is started in the registration roller pair 7 (step S14).

  Here, the timing of releasing the nip of the third skew feeding roller pair 32c is that the registration roller pair 7 conveys 10 mm during the time obtained by dividing the distance from the registration roller front sensor Q to the registration roller pair 7 by the speed of the skew feeding section 30. Is set by the soft count value plus the time required for. On the other hand, if the sensor Q before the registration roller does not detect (ON) the leading edge of the sheet S in step S11, a paper jam (delay jam) is displayed on the operation unit 412 (step S17), and the process ends.

  Next, the sheet passing counter counts the count number K = K−1 (step S15). If the count number K is not 0, the sheet S is aligned by the first to third skew feeding roller pairs 32a to 32c. At the end timing, the conveying roller pair 34 is pressurized again and the paper is passed. On the other hand, if the count number K is K = 0 (step S16), the process is terminated.

  Here, the skew feeding correction operation when the skew feeding correcting portion 55 releases only the nip N1 of the first skew feeding roller pair 32a will be described. FIG. 16 is a flowchart showing the skew correction operation when the skew correction unit 55 according to the present embodiment releases only the nip N1 of the first skew feeding roller pair 32a.

  The operation of releasing the nip of the first skew feeding roller pair 32a is the same as the operation of releasing the nip of the first skew feeding roller pair 32a after the second skew feeding roller pair 32b is pressurized by 10 mm and conveyed by 10 mm. The description is omitted here (see steps S01 to S17).

  The present embodiment can be suitably carried out when the basis weight is relatively stiff among the ultrathin coated paper, such as the coated paper having a basis weight of 70 (gsm) or more and less than 80 (gsm). For example, since the second skew feeding roller pair 32b and the third skew feeding roller pair 32c are in a nip-pressed state, in order to fix and stabilize the posture of the sheet S, the nip of the second skew feeding roller pair 32b is used. It is more stable to hold the sheet S between N2 and the nip N3 of the third skew feeding roller pair 32c. Therefore, when the sheet S has a certain degree of rigidity (for example, a basis weight of 70 (gsm) or more), the sheet S can be suitably used to achieve both high accuracy of the skew correction performance of the sheet S and stability of sheet passing. .

  Further, for example, regardless of the basis weight (gsm), the short paper (the length in the conveyance direction of the sheet S <the length in the direction orthogonal to the conveyance direction) is affected by the moment M because the weight of the sheet S is light. Easy to turn. For this reason, the present embodiment can be suitably used when the turning is large as in the case of the short paper and it is desired to further improve the skew correction of the short paper.

  Next, a control operation for controlling the skew feeding correction unit 55 of the controller 600 when there are four or more skew feeding roller pairs (n) will be described with reference to FIG. FIG. 17 is a flowchart showing a skew feeding correction operation when the skew feeding correction unit 55 according to the present embodiment has n skew feeding roller pairs.

  The release timing of the n skew feeding roller pairs 32a to 32n (the upstream skew feeding roller pair releases the nip after the downstream skew feeding roller pair presses the nip) is the first to third skews described above. Since it is the same as that of the pair of feed rollers 32a to 32c, its description is omitted here.

  The controller 600 releases the nip of the third skew feeding roller pair 32c after the leading edge of the sheet S is conveyed by 10 mm after the nipping of the fourth skew feeding roller 32d (step S100). As described above, the (n-1) th feeding roller pair (n-1) is moved to the (n-1) th feeding roller pair (n-1) after the leading edge of the sheet S is nipped between the nth feeding roller pair (n) and conveyed by 10 mm. n-1) The nip of the skew feeding roller pair (n-1) is released (step S101). Since the subsequent operation is the same as that of the first to third skew feeding roller pairs 32a to 32c, the description thereof is omitted here (steps S10 to S16 and S17).

  The image forming apparatus 100 according to the present embodiment having the above-described configuration has the following effects. In the image forming apparatus 100 according to the present embodiment, the sheet S that has been obliquely fed by the upstream (n-1) skew feeding roller pair (n-1) is nth skew feeding roller pair n arranged on the downstream side. When the sheet is nipped, control is performed so as to release nipping of the sheet S by the (n−1) -th skew feeding roller pair (n−1). For example, when the second skew feeding roller pair 32b sandwiches the sheet S that has been skew fed by the first skew feeding roller pair 32a, the image forming apparatus 100 separates the driven roller roller of the first skew feeding roller pair 32a from the driving roller. Thus, control is performed so as to release the holding of the sheet S. As a result, the deflection difference ΔL in the sheet conveyance direction and the deflection L itself can be gradually released, and the skew correction performance and the sheet passing stability can be improved. Further, skew correction can be performed even for a sheet having low stiffness (stiffness), and stable skew correction of the sheet S can be performed regardless of the type of the sheet. As a result, it becomes possible to deal with media for further thin paper.

  Conventionally, for example, the first skew feeding roller pair 32a is affected by the turning when the sheet enters the reference member 31, and the second skew feeding roller pair 32b, the third skew feeding roller pair 32c, and the like (the nth skew feeding roller pair). It was larger than the pair of feed rollers (n). Also, the nip pressurization time was the longest, and the durability life of the driving rubber roller of the first skew feeding roller pair was short. However, in the present embodiment, since the first skew feeding roller pair 32a is frequently released from the nip, the durability of the first skew feeding roller pair 32a can be improved. As a result, the cost of parts and the like can be reduced, and maintenance costs can be reduced.

  Further, in this embodiment, when the sheet S is abutted against the reference member 31 and the sheet S is abutted and aligned, the downstream side n-th inclined feeding roller pair n holds the sheet S, and then the upstream side The nipping of the sheet S of the (n-1) th skew feeding roller pair (n-1) is released. That is, the sheet S is not nipped by a plurality of skew feeding roller pairs, and the sheet S is nipped by one skew feeding roller pair. Therefore, for example, even when the pressing force of the sheet S against the reference surface is too strong and the side end portion of the sheet S bends, it becomes easy to slip and eliminate the deflection generated at the side end portion. Then, by eliminating the bending generated at the side edge of the sheet S, the posture of the sheet S at the time of abutting alignment can be matched with the sheet conveying direction. As a result, it is possible to further improve the skew feeding correction performance with thin paper and to stabilize the transportability at the time of alignment of the sheet S (improve the stability of paper passing). Further, it is possible to improve the durability of the skew feeding roller pair by releasing the nip of the skew feeding roller pair.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above. In addition, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

  For example, in the present embodiment, the skew correction unit 55 is disposed on the upstream side of the secondary transfer unit 515, but the present invention is not limited to this. In addition to the upstream side of the secondary transfer unit 515, the skew feeding correction unit can be used, for example, on the upstream side of the paper discharge system sheet post-processing apparatus after fixing.

DESCRIPTION OF SYMBOLS 30 Slope feeding part 31 Reference | standard member 32a 1st diagonal feeding roller pair 32b 2nd diagonal feeding roller pair 32c 3rd diagonal feeding roller pair 33 Fixed guide 50 Conveyance roller part 55 Skew correction | amendment part 100 Image forming apparatus 100A Image forming apparatus main body 100B Sheet feeding unit 100C Transfer unit 100D Sheet conveying unit (sheet conveying device)
331a, 331b, 331c Driven roller 332a, 332b, 332c Drive roller 513 Image forming unit 515 Secondary transfer unit 600 Controller S Sheet

Claims (6)

In Cie over preparative conveying apparatus to correct the skew of the sheet to convey the sheet conveying path,
A first pair of inclined feeding rollers such that the sheet over preparative separably to feed obliquely,
Before SL provided in the sheet conveyance direction downstream side of the first pair of inclined feeding rollers, and a second oblique-feed rollers to the first skew roller pair is fed obliquely the sheet feeding obliquely,
Provided in the sheet conveyance direction downstream side of the second oblique-feed rollers, and a third pair of inclined feeding rollers where the second pair of inclined feeding rollers to feed obliquely the sheet feeding obliquely,
A reference member that is disposed along the sheet conveyance direction and corrects the skew of the sheet by abutting the side edge of the sheet that is obliquely fed by each of the skew feeding roller pairs ;
After the sheet conveyed by pre-Symbol first skew roller pair has reached the second oblique-feed rollers, before the sheet conveyed passes through the first pair of inclined feeding rollers by the first pair of inclined feeding rollers in, and and a control unit which Ru is separated the first pair of inclined feeding rollers until reaching the third skew roller pair,
A sheet conveying apparatus. The nip pressure of the second skew feeding roller pair is set higher than the nip pressure of the first skew feeding roller pair.
The sheet conveying apparatus according to claim 1. The nip pressure of each of the skew feeding roller pairs is set so as to increase as it becomes the downstream feeding roller pair.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. The second skew feeding roller pair is configured to be contactable and separable,
When the sheet conveyed by the second skew feeding roller pair reaches the third skew feeding roller pair, the control unit moves the second skew feeding roller pair until it passes through the second skew feeding roller pair. To separate,
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. The first skew feeding roller pair, the second skew feeding roller pair, and the third skew feeding roller pair are arranged at a position where the conveyed sheets can be nipped simultaneously.
  The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. An image forming unit that forms an image on a sheet, and the sheet conveying device according to any one of claims 1 to 5 that conveys the sheet to the image forming unit.
An image forming apparatus.

Images